1. Field of the Invention
The invention relates to a vibration damper with amplitude-dependent damping force of the type having a piston rod axially movable in a cylinder and carrying a piston which divides the cylinder into two working spaces, a housing in which a separating element separates a variable volume chamber from one of the working spaces, and a flow connection which connects the chamber to the other of the working spaces.
2. Description of the Related Art
In the design of vibration dampers, there is always a compromise between a soft damping force characteristic, which emphasizes a comfortable ride, and a stiffer damping force characteristic, which emphasizes driving safety. Adjustable vibration dampers, whether switched or continuously variable, expand the possibilities, but they are much more expensive and are therefore reserved for vehicles of the luxury class.
In DE 40 02 882 C1, a hydraulic vibration damper is described, the piston rod of which is permanently connected to a housing. A membrane separates the housing into two chambers, each of which is connected to a working space of the cylinder. When the piston rod makes a short movement, the damping medium displaced from the compressed working space is pushed into the adjoining chamber of the housing, the membrane of which makes possible a slight increase in the size of the chamber. The enlargement of the chamber is a function of the amplitude of the movement of the piston rod. When the stroke of the piston rod exceeds a certain defined value, the damping medium must be displaced into the pressure-relieved working space of the cylinder through a valve connected in parallel to the chamber.
The use of the housing with the membrane makes it possible in particular to isolate effectively the high-frequency vibrations of small amplitude from the vehicle body and thus also to provide a comfortable ride even though the chassis is suspended more stiffly.
Reference can also be made to DE 100 47 878 A1, in which a rigid valve body instead of an elastically deformable membrane is used inside the housing.
From these two sources, the expert concludes that the housing, which is permanently screwed to the piston rod, is comparatively massive. In the variant according to FIG. 3 of DE 100 47 878 A1, it is also pointed out that the housing, together with the piston, can be connected by known fastening techniques to the piston rod, but in this case the housing has a load-bearing function and must be designed to have the necessary strength.